The human heart is divided into four chambers. These four chambers include the right atrium and the right ventricle, and the left atrium and the left ventricle. The heart contracts rhythmically under stimulation of electrical currents to move blood through the chambers of the heart and the remainder of the cardiovascular system.
Blood in the heart is kept flowing in a unidirectional manner through the cardiovascular system by a system of four one-way valves. As the heart cycles the valves open and close to allow blood to move one-way through the heart chambers.
The heart valves differ significantly in structure. For example, the ventricles are separated from the atria by valves that, in addition to the leaflets, have thin but strong cords of fibrous tissue. Called chordae tendineae, these cords tether the valve to the ventricular walls. When the ventricles contract, small muscles in their walls, called papillary muscles, pull the cords which act as tethers, and control the closure of the valve leaflets, preventing them from flapping too far backwards.
One such valve located between the left ventricle and the left atrium is called the mitral valve. The mitral valve has two leaflets that form the valve. The leaflets are attached to papillary muscles by way of the chordae tendineae and it allows blood to enter the left ventricle from the left atrium.
When operating properly, the mitral valve acts as a one-way valve. There are, however, numerous conditions that can cause the mitral valve to not act as a one-way valve. For example, deficiency or degeneration of one or more of the mitral valve structures may result in dysfunction of the mitral valve apparatus leading to mitral valve prolapse or regurgitation during a contraction of the heart. Prolapse or regurgitation of the mitral valve can eventually lead to severe cardiovascular problems, and even death.